The present invention relates to a semiconductor device and a method of forming the same, and more particularly to a semiconductor device having a cylindrically shaped capacitor with an improved electrode surface, and method of forming the same.
As an electrode of the capacitor in the semiconductor device, a box-shaped electrode has been known. A hemispherical grain surface is formed on a surface of the box-shaped electrode to increase a surface area of the box-shaped electrode thereby increasing a capacitance of the capacitor. It is, however, difficult to obtain a sufficient capacitance of the capacitor under the requirement for further scaling down of the semiconductor device. Under this circumstances, in place of the conventional capacitor having the box-shaped electrode, a cylindrically shaped electrode has been attracted which has a hemispherical grain surface entirely which is larger by about four times than the box-shaped stacked electrode. In Japanese laid-open patent publication No. 9-167833, it is disclosed to form a hemispherical grain surface on the entire surface of the cylindrically shaped electrode.
Formation of the hemispherical grain is progressed from both outer and inner surfaces of the cylindrically shaped electrode. In order to enlarge a grain size, it is possible that holes are grown from the outer wall toward the inner wall of the cylindrically shaped electrode, whereby the holes may penetrate the cylindrically shaped electrode. Even if the penetrating holes are not formed, it is possible that crystal grains of polysilicon penetrate from the inner wall to the outer wall of the cylindrically shaped electrode.
The above phenomenons of penetrations of the holes or the crystal grains result in reductions in mechanical strength of the stacked electrode. When a dielectric film is formed on the surface of the stacked electrode, and when an inter-layer insulator is formed, and when a heat treatment is carried out, stresses are applied to the stacked electrode, whereby it is possible that the capacitor is broken. If the hemispherical grains are formed on the outer wall of the cylindrically shaped electrode, then it may be possible that a short circuit is formed between adjacent two of the stacked electrodes.
In the above circumstances, it had been required to develop a novel semiconductor device and method of forming the same free from the above problems.
Accordingly, it is an object of the present invention to provide a novel cylindrically shaped stacked electrode free from the above problems.
It is a further object of the present invention to provide a novel cylindrically shaped stacked electrode having a hemispherical grain surface being free of any holes which penetrate from an outer wall to an inner wall of the cylindrically shaped stacked electrode and having a high mechanical strength to prevent a capacitor from being broken.
It is a still further object of the present invention to provide a novel cylindrically shaped stacked electrode having a hemispherical grain surface being free of any crystal grains which penetrate from an outer wall to an inner wall of the cylindrically shaped stacked electrode and having a high mechanical strength to prevent a capacitor from being broken.
It is yet a further object of the present invention to provide a novel semiconductor device having a capacitor having an improved cylindrically shaped stacked electrode free from the above problems.
It is further more object of the present invention to provide a novel semiconductor device having a capacitor having an improved cylindrically shaped stacked electrode having a hemispherical grain surface being free of any holes which penetrate from an outer wall to an inner wall of the cylindrically shaped stacked electrode and having a high mechanical strength to prevent a capacitor from being broken.
It is moreover object of the present invention to provide a novel semiconductor device having a capacitor having an improved cylindrically shaped stacked electrode having a hemispherical grain surface being free of any crystal grains which penetrate from an outer wall to an inner wall of the cylindrically shaped stacked electrode and having a high mechanical strength to prevent a capacitor from being broken.
It is another object of the present invention to provide a novel method of forming a cylindrically shaped stacked electrode free from the above problems.
It is a further object of the present invention to provide a novel method of forming a cylindrically shaped stacked electrode having a hemispherical grain surface being free of any holes which penetrate from an outer wall to an inner wall of the cylindrically shaped stacked electrode and having a high mechanical strength to prevent a capacitor from being broken.
It is a still further object of the present invention to provide a novel method of forming a cylindrically shaped stacked electrode having a hemispherical grain surface being free of any crystal grains which penetrate from an outer wall to an inner wall of the cylindrically shaped stacked electrode and having a high mechanical strength to prevent a capacitor from being broken.
It is yet a further object of the present invention to provide a novel method of forming a semiconductor device having a capacitor having an improved cylindrically shaped stacked electrode free from the above problems.
It is further more object of the present invention to provide a novel method of forming a semiconductor device having a capacitor having an improved cylindrically shaped stacked electrode having a hemispherical grain surface being free of any holes which penetrate from an outer wall to an inner wall of the cylindrically shaped stacked electrode and having a high mechanical strength to prevent a capacitor from being broken.
It is moreover object of the present invention to provide a novel method of forming a semiconductor device having a capacitor having an improved cylindrically shaped stacked electrode having a hemispherical grain surface being free of any crystal grains which penetrate from an outer wall to an inner wall of the cylindrically shaped stacked electrode and having a high mechanical strength to prevent a capacitor from being broken.
The first present invention provides a cylindrically shaped stack electrode having a lamination structure which comprises a cylindrically shaped outer layer and a cylindrically shaped inner layer laminated on an inner wall of said cylindrically shaped outer layer, wherein hemispherical grains are formed on an inner wall of said cylindrically shaped inner layer.
The above and other objects, features and advantages of the present invention will be apparent from the following descriptions.